With increasing development of an inkjet technology, the inkjet technology is not only used in the traditional printer market but also used in flat panel displays and semiconductor manufacturing processes in recent years. However, for reducing the fabricating cost and saving the process time, researchers are seeking new inkjet technologies. As known, a piezoelectric inkjet technology is one of the most widely-used new inkjet technologies.
Please refer to FIGS. 1A, 1B and 1C. The inkjet head manufactured by the conventional piezoelectric inkjet technology has a multilayered structure 1. The multilayered structure 1 is formed by perform a metal fusion bonding process to stack several layers of stainless steel plates. The multilayered structure 1 comprises a plurality of inkjet units 10. Each inkjet unit 10 comprises an inlet flow channel 101 for introducing an ink liquid, an ink chamber 102 for storing the ink liquid, a pressure cavity 103, an outlet flow channel 104, a nozzle hole 105 and other microstructures. In addition, a vibration film plate 106 is disposed over the inlet flow channel 101, the ink chamber 102, the pressure cavity 103, the outlet flow channel 104 and the nozzle hole 105 of each inkjet unit 10. Corresponding to the location of the pressure cavity 103, an actuator plate 107 is disposed over the vibration film plate 106. Since the inkjet unit 10 is formed by stacking several layers of stainless steel plates, the dimension precision of fabricating the stainless steel plates should meet with stringent requirements. Moreover, during the process of assembling these stainless steel plates, the assembling error should be controlled to be lower than an acceptable level. If the assembling error is too high, the outlet flow channel 104 corresponding to the nozzle hole 105 is readily blocked. In addition, the nozzle hole 105 is usually produced by etching a nozzle hole plate with a thickness smaller than 200 micrometer and a tolerance around 10 micrometer, the edge size of the nozzle hole plate is readily changed because of etchant concentration, etching time or other parameters. Due to the assembling error of assembling so many layers of stainless steel plates, the nozzle hole 105 is prone to dislocation. That is, the location of the nozzle hole 105 is deviated. Under this circumstance, the outlet flow channel 104 is shrunken and becomes non-upright, and thus it is difficult to eject the ink. In addition, since the ink droplets of the ink liquid are not uniformly-sized, the printing quality is deteriorated.
The conventional inkjet unit 10 is assembled by the metal fusion bonding process. Hereinafter, the process of assembling the conventional inkjet unit 10 will be illustrated as follows. Firstly, the surfaces of the stainless steel plates are plated with gold. Then, these plates are successively stacked together in the predetermined order. Then, a thermal compression process is performed to diffuse the gold atoms between every two adjacent plates. Afterwards, the fusion bonding action of these plates is completed. Although this assembling process has good bonding efficacy, there are still some drawbacks. For example, since the fusion bonding process is carried out at a high temperature (e.g. 500˜1000° C.) under the anaerobic environment, it is difficult and expensive to install the equipment. In addition, the heating jig for facilitating thermal compression should be carefully selected. If the heating jig is not proper, the heating jig is easily suffered from deformation, degradation or even crack. That is, since the heating jig is severely cracked or adhered, the depletion rate is very fast. In addition to the high replacement cost of the heating jig, the mass production quality is unstable. As known, gold is increasingly expensive, the fusion bonding process is not easily in a batch-wise manner, and the fusion bonding efficacy and yield are affected by the surface treatment. Due to these reasons, the fabricating cost of producing the inkjet units by the metal fusion bonding process is gradually increased.
After the actuator plate 107 is stacked as the uppermost layer of the multilayered structure 1, the actuator plate 107 is cut according to the profile of the pressure cavity 103. The resulting structure of the inkjet head with a plurality of inkjet units 10 is shown in FIG. 1B. During the process of cutting the actuator plate 107 of the multilayered structure 1, the inkjet units 10 are classified into a first inkjet unit group 11 and a second inkjet unit group 12. The inkjet units 10 of the first inkjet unit group 11 and the second inkjet unit group 12 are arranged in a staggered form. In addition, the pressure cavity of each inkjet units 10 in the actuator plate 107 has a rectangular rim 133.
Generally, the actuator plate 107 is cut by a laser cutting process. Please refer to FIG. 1D, which schematically illustrates the multilayered structure of a conventional inkjet head before a laser cutting process is performed. For performing the laser cutting process, the rectangular rims 133 of the inkjet units 10 of the first inkjet unit group 11 and the second inkjet unit group 12 should be precisely positioned one by one. Then, the actuator plate 107 is cut into a plurality of small actuator pieces corresponding to the locations of the pressure cavities 103 of respective inkjet units 10. During the laser cutting process is performed, the cutting positions should be precisely controlled and the power needs to homogenized, the rectangular rims 133 of the inkjet units 10 should be precisely aligned, and the cutting depth and width should be precisely controlled. If the cutting depth is too large, the vibration film plate 106 underlying the actuator plate 107 is possibly damaged. Whereas, if the width is improperly controlled, the adjacent inkjet units 10 are adversely affected. Consequently, before the laser cutting process is performed, the laser wavelength, energy, duration and other parameters should be preset in order to achieve the desired size of the actuator plate 107. In other words, before the laser cutting process is performed, it is time-consuming and complicated to set these cutting parameters.
For producing the plurality of actuator pieces by the laser cutting process, the rectangular rims 133 are cut one by one. Since the inkjet units 10 of the first inkjet unit group 11 and the second inkjet unit group 12 are arranged in a staggered form, the laser cutting action needs to be stopped whenever one of the rectangular rims 133 is cut. The next laser cutting action is done when the next rectangular rim 133 is aligned. Since it takes much time to repeatedly align the start point of each actuator pieces, the conventional process of cutting the actuator plate 107 is very long. Moreover, since the cutting speeds at the start point, end point or the turning portion are different, the non-homogeneous power usually results in uneven cutting depth, low yield and high cost.
Moreover, the laser machine is more expensive than other cutting machines. If the laser power is unstable during the laser cutting process is performed, a great deal of heat will be generated. Under this circumstance, the magnetic flux intensity and the physical intensity of the actuator plate 107 are adversely affected.
Therefore, there is a need of providing an improved method of manufacturing an inkjet head so as to obviate the drawbacks encountered from the prior art.